Hello!
For a Uni project I'm making an automated guitar tuner. I've got almost everything in place I just need to get the motor to spin the tuning peg.
I have this motor http://www.ebay.co.uk/itm/DC-12V-14...r-UK-SELLER-/281929603585?hash=item41a4505a01
And the best I could do was to drill a hole into a highlighter lid and slip it over the motor shaft and put a screw through to hold it in place which worked! But the plastic has begun to tear open and it's now useless. Metal is stronger than plastic. I've attached a picture of my attempt.

@DonnellyCircuits
It seems like the body of a BIC lighter or PEZ dispenser could fit. The BIC lighter is stronger but more dangerous to open up (residual fluid will be flammable). I think the fat (large capacity) style will fit a key.

Or, get a piece of hardwood and drill two 3/8" holes next to each other to make an oval. The cut around them to make the part. Drill a though-hole to allow mounting to the motor. Epoxy a flat metal base plate to the bottom to with a "key" to the flat spot on the motor to insure it does not get rounded out. I hope you could understand that because it made perfect sense in my head.

Hello!
For a Uni project I'm making an automated guitar tuner. I've got almost everything in place I just need to get the motor to spin the tuning peg.
I have this motor http://www.ebay.co.uk/itm/DC-12V-14...r-UK-SELLER-/281929603585?hash=item41a4505a01
And the best I could do was to drill a hole into a highlighter lid and slip it over the motor shaft and put a screw through to hold it in place which worked! But the plastic has begun to tear open and it's now useless. Metal is stronger than plastic. I've attached a picture of my attempt.